Determination of N tau-methylhistamine in plasma and urine by isotope dilution mass fragmentography.

The determination in N tau-methylhistamine by gas chromatography-mass spectrometry is described using bis-heptafluorobutyryl derivatives and deuterium labelled N tau-methylhistamine as internal standard. A description of the synthesis of the internal standard, N tau-trideuteromethylhistamine, is given. Normal concentrations for plasma were 1.4 +/- 0.4 microgram/l (mean +/- 1 S.D., n = 10). The normal values for urine ranged from 60 to 280 microgram/24 h (n = 20). Five asthmatic patients showed above-normal plasma concentrations.